1. Field of the Invention
The invention relates to a monolithic support for full-surface support of a workpiece.
2. Description of Related Art
In the manufacturing of large-sized workpieces made of brittle or hard and brittle material, for example in the manufacturing of mirror carriers made of glass, glass ceramics, or ceramics, the actual fabrication of the mirror carrier will be followed by further processing steps such as grinding and drilling, polishing, coating. In order to avoid damage to the mirror carrier which is usually produced in a very complex and therefore expensive procedure, it has to be supported in subsequent processing steps. Supports are also necessary for transportation of such systems in order to prevent damage to the workpiece.
Hitherto, steel support structures have been used to support thin mirror carriers. However, a drawback of such support structures is that they do not provide for full-surface support of the supported workpiece so that it may happen in this case that the supported workpiece does not retain its shape but is deformed under the influence of external forces, for example under the effect of gravity.
This is particularly important when the workpiece is a mirror carrier having a very large aspect ratio of 50 or more. Here, the aspect ratio is defined as the ratio of the diameter of the mirror carrier to the average thickness thereof. The high aspect ratio generally also implies a low basis weight.
EP 1 391 433 A2 discloses a mold, by way of example, onto which a glass or glass-ceramic mirror carrier blank may be allowed to sag under gravity, the mold itself being made of a keatite glass ceramic.
Such a keatite glass ceramic mold has a number of advantageous properties, for example very high temperature resistance. However, the manufacturing of such a mold or support for a mirror carrier involves great complexity and accordingly elevated costs. That is, first a block is cast from a molten glass and is subsequently transformed into a high quartz mixed crystal glass ceramic in a first so-called ceramization step. Then, an appropriate blank is mechanically cut out of the so obtained block and is finally transformed into a keatite mixed crystal glass ceramic in another ceramization step. In order to ensure adequate surface quality of the so obtained mold, the mold is again processed mechanically and then lapped. The complex production process implies high costs, so that although such a glass ceramic support is in principle suitable for producing mirror carrier substrates, it is however ruled out for being used for transporting such substrates and for remaining with the customer. Moreover, the option of producing structures in the surface, for instance in the form of filigree surface patterns, is complicated due to the multi-stage production processes for a glass ceramic mold.
Therefore, there is a need for a support for supporting large-sized workpieces over substantially the entire surface, in particular workpieces having an aspect ratio of 50 or more, which support should ensure dimensional stability of the workpiece during finishing and transportation, and it should be producible with a structured surface.